Temporary Anchorage Device (TAD) use in the treatment of anterior open bite

While orthognathic surgery is sometimes the only option to treat certain skeletal malocclusions, having another tool in the arsenal is a welcome option for patients and clinicians alike. Recently, the minimally invasive placement of temporary anchorage devices (TADs) has allowed orthodontists to treat some of these patients without orthognathic surgery through intrusion of the posterior maxillary molars. The TAD can be loaded immediately as it gains its anchorage through mechanical gripping of bone rather than through osseointegration. Dr. Padraig Dennehy presents a case in which TADs are used to treat an anterior open bite.

While orthognathic surgery is sometimes the only option for treatment of certain skeletal malocclusions, having another tool in the orthodontist’s arsenal is a welcome option for patients and clinicians alike. Anterior open bite, defined as a state in which the maxillary and mandibular molars occlude first in mandibular closure, leaving the anterior teeth out of contact (1), has previously been treated by a variety of means. These treatments include but are not limited to extractions, high-pull headgear, bite blocks, elastics, and functional appliances (2). In more severe cases, the patient may require orthognathic surgery to correct the skeletal malocclusion. In cases of anterior open bite due to overeruption of the maxillary posterior teeth (posterior maxillary vertical excess), the oral surgeon will reposition the posterior maxilla superiorly, allowing autorotation of the mandible upward and forward to close the open bite (2). Orthognathic surgery is a predictable treatment modality for anterior open bite cases, but is sometimes cost prohibitive and has associated risks and recovery time.

Recently, the minimally invasive placement of TADs (temporary anchorage devices) has allowed orthodontists to treat some of these patients without orthognathic surgery through intrusion of the posterior maxillary molars. While TADs are not a substitute for surgery in all cases, they do provide a treatment alternative for specific mild-to-moderate open bite cases without other skeletal malformations.

TADs are titanium-alloy mini-screws that range from 6–12 mm in length and 1.2–2 mm in diameter (3). The orthodontist or surgeon can insert the TAD directly into the bone through the gingiva with a handheld driver and, most often, with the use of only topical anesthetic (3). The TAD can be loaded immediately as it gains its anchorage through mechanical gripping of bone rather than through osseointegration (3).

In the case of anterior open bites, TADs are placed bilaterally on the buccal aspect of the maxilla between the second premolar and first molar. The greatest amount of interradicular bone in the posterior maxilla is found in this region, about 5–8 mm from the alveolar crest (3). In the case of less-than-ideal interradicular bone, the TAD could be placed palatally or roots can be diverged before TAD placement (3). The maxillary molars and premolars are banded and bracketed respectively and ligated with bilateral, segmented stainless steel wires. Once levelling and aligning of these teeth are complete, the TAD is placed and a nickel titanium coil and elastic chain are used to connect the TAD to the mesial of the first premolar and hook of the second molar band. This creates a light and continuous force to produce intrusion en masse of the first premolar to the second molar bilaterally.

In conjunction with TAD placement, a TPA (transpalatal appliance) is placed to prevent the intruding molars and premolars from tipping buccally (3). An acrylic button is placed on the center of the TPA and the patient is instructed to press occasionally on the button with the tongue. Tongue pressure on the TPA also aids in tooth intrusion (3).

Case reportA healthy 15-year-old male presents to the clinic with an anterior open bite. His case is outlined in the figures below.

Figure 1: Pretreatment photos of 15-year-old male exhibiting a 3 mm anterior open bite. Figure 2: Treatment photos prior to TAD placement. Leveling and aligning of maxillary posterior teeth only. Note the two-plane occlusion in the maxillary arch where the anterior and posterior teeth occupy two very different planes of occlusion.

Figure 3: Once the leveling and aligning of the maxillary posterior teeth has been accomplished, the patient is now ready for TAD placement and TPA delivery. PAN was taken in bitewing mode post. TAD insertion to verify there is no impingement of roots on adjacent teeth.Figure 4: Photos show elastic chain and open coils creating intrusion forces on maxillary premolars and molars. Photos were taken three months after TADs were placed and OB has improved by 1 mm.Figure 5: Photos taken seven months after TAD placement. Patient now has some positive OB on upper central incisors. Note the position of the TAD relative to the molars compared to the photos in Figure 4. This relative position change is due solely to intrusion of the maxillary posterior teeth.

The patient in the above case report is still in active treatment. Now that successful maxillary posterior intrusion has been accomplished, the remaining full, fixed orthodontic appliances can be placed. The TPA can be removed and the molar intrusion will be held for the remainder of treatment with a ligature tie placed from the first molar to the TADs. The TADs will be kept in place for the remainder of treatment to maintain the stability of the intrusion as bone remodeling occurs.

In terms of stability of anterior open bite treatment using TADs to intrude the posterior maxillary teeth, a study by Baek et al. showed that the relapse of the incisal overbite was 17% in the first year post deband (4). Three year follow-up was done on these same patients and no further significant relapse was noted (4). Thus, relapse appears to be most common during that first year, and as such an appropriate retention protocol with strong patient compliance is important in terms of outcome of this treatment.

More studies are needed to determine whether treatment of anterior open bites with TADs will stand the test of time, but what is known for sure is that if given the option, many patients will benefit from this nonsurgical approach as a viable treatment option for their malocclusion.

Padraig Dennehy, DMD, is a fourth-generation Montanan, having been born and raised in Butte, Montana. He attended Montana Tech of the University of Montana, graduating summa cum laude with a major in biology and a minor in mathematics. Dr. Dennehy obtained his dental degree from Harvard School of Dental Medicine in June 2007. Following Harvard, he completed a two-year residency program in the specialty of orthodontics at the University of Minnesota. Prior to returning to Montana, he practiced orthodontics in Minnesota for two years. He is a member of the cleft lip and palate team, working in conjunction with other professionals to treat craniofacial patients who require specialized care. When he is not treating patients, Dr. Dennehy enjoys playing tennis, racquetball, mountain biking, hiking, trivia, and playing with his Siberian Husky, Dublin.